1. Technical Field
The present invention relates to a vertical cavity surface emitting laser and an atomic oscillator.
2. Related Art
The vertical cavity surface emitting laser (VCSEL) is, for example, used as a light source of the atomic oscillator using coherent population trapping (CPT) which is one of the quantum interference effects.
In the vertical cavity surface emitting laser, a resonator generally has an isotropic structure, and accordingly it is difficult to control a polarization direction of laser light emitted from the resonator. JP-A-11-54838, for example, discloses a vertical cavity surface emitting laser which generates distortion in a resonator by a distortion imparting portion and causes double refraction to occur, so as to stabilize a polarization direction of laser light obtained by laser oscillation.
However, in the vertical cavity surface emitting laser disclosed in JP-A-11-54838, a positional relationship between the distortion imparting portion and a bonding pad of an upper electrode has not been considered. Accordingly, in the vertical cavity surface emitting laser disclosed in JP-A-11-54838, the distortion imparting portion may be damaged when performing wire bonding. When the distortion imparting portion is damaged, stress applied to a vertical resonator is not sufficient, and thus the polarization direction of the laser light may not be stabilized.